Surge voltage arrester assembly having integral capacitor mounting and connecting means

ABSTRACT

A sparkgap assembly for a low-voltage lightning arrester is provided with a sparkgap-shunting capacitor mounting and connecting means that is an integral part of the sparkgap assembly. The integral capacitor mounting and connecting means comprises a highly reliable yet economically manufactured arrangement that is well adapted to mass production techniques for making lightning arresters.

United States Patent l l l Earl M. Stetson;

Thomas J. Carpenter, both of Pittstield, Mass.

Jan. 12, 1970 Nov. 9, 197 1 General Electric Company Inventors Appl. No.Filed Patented Assignee SURGE VOLTAGE ARRESTER ASSEMBLY llAVING INTEGRALCAPACITOR MOUNTING ANI) CONNECTING MEANS 16 Claims, 6 Drawing Figs.

US. Cl 315/36, 315/59, 313/231.1, 317/61 Int. Cl "02h 7/24, HOZh 9/06Field 01 Search 315/36, 59;

Primary ExaminerHerman Karl Saalbach Assistant Examiner-SaxfieldChatmon, .Ir.

Attorneys-Vale P. Myles, Francis X. Doyle, Frank L.

Neuhauser, Oscar B. Waddell and Joseph B. Forman ABSTRACT: A sparkgapassembly for a low-voltage lightning arrester is provided with asparkgap-shunting capacitor mounting and connecting means that is anintegral part of the sparkgap assembly. The integral capacitor mountingand connecting means comprises a highly reliable yet economicallymanufactured arrangement that is well adapted to mass productiontechniques for making lightning arresters.

SURGE VOLTAGE ARRESTER ASSEMBLY HAVING INTEGRAL CAPACITOR MOUNTING ANDCONNECTINGMEANS It is known in the prior art to shunt connect acapacitor across one or more of the sparkgaps in a multigap sparkgap assembly in order to effectively short circuit the shunted gaps when onovervoltage, high-frequency surge is initially impressed across theassembly. Such upsetting" of the sparkgap assembly voltage distributioncauses a disproportionately high voltage to be applied across theremaining, unshunted gaps of the assembly and thereby forces these gapsto breakdown and sparkover at a relatively lower voltage than thesparkover voltage rating of the assembly without such capacitanceupsetting. A major advantage of upsetting circuits for sparkgapassemblies is that a lower sparkover voltage can be obtained for a givenarrester rating.

It has been common practice in prior art sparkgap assemblies to mountupsetting capacitors adjacent the outer surface of the assembly housingand to connect the respective capacitor terminals in shunt with theassemblys sparkgaps by soldering wire leads thereto, or by mechanicallyfastening conductive wires or bands to the respective electrode formingthe shunted sparkgap. Although such mounting and connecting arrangementsare relatively expensive and require substantial free space within thehousing for a sparkgap assembly, these problems have not prevented theuse of such circuits in highvoltage station lightning arresterswhereadequate space exists within the lightning arrester housing for suchcapacitors and wherein the relative expense of such connectors is asmall factor in the overall cost of manufacturing these arresters.However, heretofor the prior art mounting and connecting means forshunting capacitors have precluded their use in relatively inexpensive,compactly built low-voltage distribution lightning arresters.

In one preferred form of our invention, a sparkgap assembly is providedfor a low-voltage distribution type of lightning arrester that ischaracterized by incorporating a sparkgap-shunting, upsetting capacitorthat is operative to reduce the sparkover voltage of the assembly when ahigh-voltage surge is impressed across it. The capacitor is mountedwithin the sparkgap assembly and forms an integral part of this assemblyso that additional space is not required within an arrester housing forthe assembly to accommodate the capacitor. Also, unique means areprovided for economically and reliably afiording an electricalconnection between the respective terminals of the capacitor and theelectrodes forming the shunted sparkgap of the assembly.

A primary object of our invention is to provide a sparkgap assembly fora low-voltage distribution lightning arrester that is less expensive tomanufacture than prior art distribution lightning arresters and at thesame time possesses superior operating characteristics.

Another object of the invention is to provide a reliable and inexpensivecapacitor mounting arrangement and connecting circuit for shunting acapacitor across predetermined electrodes of a sparkgap of a sparkgapassembly.

A further object of the invention is to provide a capacitance mountingand connecting arrangement for a sparkgap assembly that can beeconomically produced on a mass production basis.

Yet another object of the invention is to provide a capacitance mountingarrangement for a sparkgap assembly in which the sparkgap formingelectrodes of the assembly serve to support the capacitor in apredetermined operating position.

A still further object of the invention is to provide a capacitormounting and connecting means for a sparkgap assembly that facilitateseasy adjustment of capacitance valves without requiring any soldering orcutting operations to make such changes.

Further objects and advantages of the invention will become apparentfrom the description that follows taken in conjunction with the drawingsappended hereto in which:

FIG. 1 is an exploded perspective view of the component parts of asparkgap assembly and capacitance voltage distributing arrangementconstructed pursuant to the teachings of our invention.

FIG. 2 is a perspective view showing the component parts of the sparkgapassembly illustrated in FIG. I in their assembled, operative positionmounted on a block of nonlinear resistance valve material.

FIG. 3 is a side elevation, cross-sectional view of the sparkgapassembly and nonlinear valve block depicted in FIG. 2.

FIG. 4 is a top plan view of a sparkgap electrode and capacitanceconnecting and supporting means, constructed pursuant to our invention,that can be utilized with a sparkgap assembly of the type illustrated inFIGS. 1-3.

FIG. 5 is a side elevation, cross-sectional view along the plane 5-5 ofthe sparkgap electrode and capacitor supporting and connecting memberillustrated in FIG. 4.

FIG. 6 is a perspective view of the electrode member depicted in FIGS. 4and 5.

Referring now to FIGS. 1 and 2 of the drawing, there is shown a sparkgapassembly 1 comprising a plurality of stacked insulating plate members 2and 3 and a plurality of generally flat, elongated sparkgap electrodes4, 5 and 6. The two end electrodes 4 and 6 are provided with integralcup-shaped terminal portions 4a and 6a, respectively, while intermediateelectrode 5 has a pair of such cup-shaped terminal portions 5a and 5bextending in opposite directions from its generally flat body portion.Each of the insulating plate members 2 and 3 are provided with apertures7 and 7', respectively, therethrough. When these component parts areassembled in operative position, as shown in FIG. 2, the cup-shapedterminal portions of electrodes 46 extend partially into the apertures 7and 7' to form sparkgaps therein with the terminal portions of electrode5 as is perhaps best seen in FIG. 3 of the drawing. Thus, a sparkgap4a-5b is formed between terminal portions 40 and 5b of electrodes 4 and5, while a second sparkgap 5a-6a is formed between the cup-shapedterminal portions 5a and 6a of electrodes 5 and 6, respectively.

It will be appreciated by those skilled in the art that various meansmay be utilized for making terminal connections to the end electrodes 4and 6 of sparkgap assembly I; however, in the embodiment of theinvention depicted in FIGS. I and 2 a pair of end terminal plates 8 and9 are mounted over the end electrodes 4 and 6 so that the base portionsof the terminal plates 8 and 9 are in electrical contact with therespective ends of electrodes 4 and 6 remote from their sparkgap-formingterminal portions 4a and 6a. The leg portions of terminal plates 8 and 9are provided with positioning apertures 10 and 10' respectively thatcooperate with preformed abutrhents 10a and 100' on the top and bottomsurfaces, respectively, of insulating plate members 2 and 3 to retainterminal plate members 8 and 9 in operative position when thesecomponent parts are assembled as shown in FIG. 2.

The sparkgap components described thus far are similar to structuralarrangements already known in the lightning arrester sparkgap art, atleast to the extent indicated in a copending US. Pat. application Ser.No. 886,l02, filed Dec. 18, 1969 by Stetson et al. and assigned to theassignee of the present invention.

Further examination of the structures shown in FIG. I and FIG. 3 willreveal that both of the insulating plate members 2 and 3 are providedwith passageways I1 and I2, respectively, therethrough. As will becomeapparent from the following description, the passageway I2 is notnecessary to the operation of the embodiment of our invention describedwith reference to FIGS. 1-3; however, it has been found that there aresubstantial economies to be realized from standardizing theconfiguration of insulating plate members 2 and 3 by providing suchpassageways (12) in each of them, and these passageways do not impairthe proper operating functions of sparkgap assembly I. Moreover, byproviding passageways, like passageway 12, in each plate member it ispossible to shunt any desired number of sparkgaps in the assembly.

When sparkgap assembly I has its components arranged in operativeposition, as shown in FIG. 3, a cylindrically shaped capacitor 13 ismounted within the passageway 11 and rests on the inner surface ofcup-shaped terminal 511. In order to facilitate a description of ourinvention, it is described hereinafter in relation to capacitor 13, butthose skilled in the art will understand that other suitable electricalimpedance devices may be used to achieve any desired voltage upsetting.For example, instead of a single capacitor 13, a resistor 13' might bemounted in passageways 11, 12, etc. as described below with reference toFIG. 5, or various combinations of resistors and capacitors in eitherseries or parallelconnected arrangements may be mounted with the uniquesupporting and connecting means of our invention to provide any desiredupsetting of a given sparkgap assembly. The passageway 11 issufficiently large to allow the capacitor 13 or a parallel capacitor andresistor coupling to be easily inserted into it but it has asmall-enough diameter to maintain capacitor 13 or such a parallelimpedance arrangement in a relatively fixed predetermined positionwithin terminal a, as best seen in FIG. 3 of the drawing. Electricalcircuit means in the form of an electrically conductive leaf spring 14is positioned in a channel formed in the'upper surface of insulatingplate member 2. In this embodiment of the invention, the width ofchannel 15 is sufficient to allow the leaf spring 14 to be compressed byelectrode 4 when the component parts of sparkgap assembly 1 are inoperative position, but is narrow enough to prevent the spring 14 frombeing rotated in a plane parallel to plate member 2 through an angle ofmore than a few degrees, as shown in FIGS. 2 and 3. Accordingly, leafspring 14 simultaneously provides good electrical conductance from theupper conductive terminal 13a of capacitor 13 and, simultaneously,resiliently biases the bottom terminal 13b of capacitor 13 intoelectrically conducting relation with the sparkgap-forming terminalportion 5a of electrode 5.

The capacitance of capacitor 13 is selected so that the veryhigh-frequency voltages of the type accompanying an overvoltage surgeresult in substantial capacitive current flow through capacitor 13. Atthe same time, the capacitance value of capacitor 13 must be such thatat normal line frequencies very low capacitive currents flow throughcapacitor 13. Therefore, the voltage distribution of sparkgap assembly 1will be upset" on high-frequency impulses and remain comparativelyuniform at normal line frequencies. Thus, it will be appreciated thatfor various applications of sparkgap assembly 1 the value of capacitor13 should be varied. A significant feature of our invention is that thesimplified capacitor mounting and electrical connecting means it affordsmake it a simple matter to exchange capacitors of different ratings.Also, it will be apparent that our invention provides another importantadvantage insofar as one or more of the sparkgaps of a multigap sparkgapassembly can be readily shunted by utilizing one or more capacitances inthe plural passageways 11, 12 etc. Of course, in the two-gap embodimentof the invention depicted in FIGS. 1-3, only one capacitor 13 isutilized because it would be undesirable to essentially short circuitboth sparkgaps 4a-5b and Sal-6a; however, if additional sparkgaps wereinserted in series with these two sparkgaps of assembly 1, then it mightbe desirable to provide capacitance shunting means for two or more ofthe gaps to properly upset" sparkgap assembly l for a given protectivefunction. It will be noted that in the embodiment of the inventiondepicted in FIGS. 1-3 the longitudinal axis of passageway 11 ispositioned concentrically over the cup-shaped terminal portion 5a ofelectrode 5 so that the strike over distance between the generally flatportion of electrode 4 and any portion of electrode 5 is alwayssubstantially greater than the sparkover distance of sparkgap 40-51;.

In the operation of the embodiment of our invention depicted in FIGS.1-3, the sparkgap assembly 1 will normally be positioned on a block ofnonlinear resistance valve material, such as block 16, and mountedwithin a lightning arrester housing either by itself or in series withother sparkgap assemblies and pieces of nonlinear resistance valvematerial (not shown). Within such an arrester, suitable circuit meansare provided to electrically connect the block of valve material 16 to aground potential terminal and to connect terminal plate 8 to anelectrical circuit that is to be protected from over voltage surges bythe operation of the arrester. Assuming such connections have been made,when a high-frequency voltage surge of predetermined value, such as alightning impulse, is impressed on end terminal 8 the voltage acrosssparkgap Ia-5b will be low and most of the voltage will appear acrosssparkgap 5a-6a because the capacity of plate 3 in combination withelectrodes 5 and 6 is much less than the capacity of capacitor 13. Thus,sparkgap 5a-6a will sparkover first followed immediately by sparkover ofsparkgap 4a-5b. After the initial high-frequency surge is discharged,the lower frequency follow current will flow through sparkgaps 4a-5b andSa-6a creating a dual homgap effect in the sinuous path from electrode 4through electrode 6 to end plate 9. Accordingly, the arcs formed insparkgaps 4a-5b and 5a-6a are rapidly lengthened to enable sparkgapassembly 1 to reseal the current path to ground.

Now that the structure and operation of one embodiment of our inventionhas been described, reference is made to FIGS. 4, 5 and 6, whichillustrate a second embodiment of an end terminal plate that is adaptedfor use with a sparkgap assembly having insulating plates and anintermediate electrode similar to the plates 2 and 3 and electrode 5 ofthe embodiment of the invention described above with reference to FIGS.1-3. Since it will be readily apparent to those skilled in the art thatthe end plate 17 depicted in FIGS. 4-5 can be substituted for thecombined end plates 8 and 9 and end electrodes 4 and 6 to form asparkgap assembly similar to assembly I, only the unique features ofterminal plate 17 will be discussed without reiterating the othercomponent parts of such an assembly. Accordingly, it can be seen thatterminal plate 17 comprises a generally U-shaped member having agenerally flat base portion 17d with three integral legs 17a, 17b and17c extending outward from one side thereof. It should be noted that leg17b is disposed in a plane below that of 17a and 17c in order to providethe proper homgap effect between electrode leg 17b and the nextintermediate electrode similar to electrode 5 of FIG. 1. A cup-shapedterminal portion 18 is formed in central leg 17b to provide thesparkover terminal of a sparkgap, in the manner that the cup-shapedterminal portion 40 on electrode 4 does in the embodiment of theinvention described with reference to FIG. 1. Within the area of theterminal plate 17 defined by an extension of the edges of central legportion 17b across its base portion 17d, an integral resilient tongue 19is formed by stamping a U-shaped arc in the electrode 17 and bending thetongue 19 so that its outer end normally rests in a plane below thegenerally flat plane of electrode 17, as best seen in FIG. 5. Therefore,when end electrode 17 is mounted in operative position on one end of asparkgap assembly over an insulating plate such as plate 2 of the FIG. 1embodiment of the invention, tongue 19 is in electrical contact with oneterminal of a capacitor like 13, also designated in FIG. 5 as capacitor13, and with a parallel resistor 13' to bias these elements intoconducting relationship with the cup-shaped terminal portion of theintermediate electrode positioned under the other terminal of capacitor13 and resistor 13. It should be understood that capacitor 13 andresistor 13' in FIG. 5 would be mounted in the same manner as capacitor13 in the embodiment of the invention shown in FIG. 3..

Of course, aside from the particular electrical connecting means andcapacitor biasing function afforded by integral tongue 19, a sparkgapassembly constructed with the end electrode plate 17 of our inventionwill operate in substantially the same manner as the embodiment of theinvention discussed above with reference to FIGS. 1-3, therefore, thissequence of operation need not be repeated.

It will be apparent to those skilled in the art that various additionalmodifications and embodiments of our invention may be made withoutdeparting from the spirit of the invention and all such variations areintended to be encompassed within the true spirit and scope of thefollowing claims. For example, it will be apparent that rather thanutilizing a leaf spring similar to leaf spring l4 other resilientconductive arrangements might be utilized to afford the capacitorsupporting and electrical connecting means taught by our invention.

What we claim as new and desire to secure by letters patent of theUnited States is:

l. A sparkgap assembly for a surge voltage arrester comprising aplurality of stacked insulating plate members, means defining anaperture through each of said plate members, a plurality of sparkgapelectrodes mounted respectively adjacent opposite sides of said platemembers over said apertures thereby to forma sparkgap in each of saidapertures between adjoining electrodes, an impedance device, electricalcircuit means connecting said impedance device in shunt relation withone of said sparkgaps, means spaced apart from said aperture defining apassageway through the plate member separating the electrodes formingsaid one sparkgap, said impedance device being mounted in saidpassageway and maintained in a predetermined relatively fixed positionby the walls thereof.

2. A sparkgap assembly as defined in claim 1 wherein said passageway islonger than the length of said one sparkgap thereby to prevent sparkoverof said passageway when a surge voltage is discharged through thesparkgap assembly.

3. A sparkgap assembly as defined in claim 1 including a resistormounted in said passageway and electrically connected in shuntrelationship with said impedance device.

4. A sparkgap assembly as defined in claim 1 wherein said circuit meanscomprises an electrically conductive spring that is resilientlycompressed between said impedance device and one of the electrodesforming said one sparkgap when assembled in operative position therebyto form a conductive circuit between said one electrode and one terminalof said im pedance device and to resiliently bias a second terminal ofsaid impedance device into conductive relationship with the otherelectrode forming said one sparkgap.

5. A sparkgap assembly as defined in claim 4 wherein said spring is aleaf spring, and including holding means for retaining said leaf springin its operative position, said holding means comprising means definingan elongated channel in the surface of the insulating plate memberimmediately adjacent the leaf spring, said channel being wide enough toallow the spring to be compressed without being retarded in suchmovement by the sidewalls of the channel but being narrow enough toprevent the spring from being rotated more than 459.

6. A sparkgap assembly as defined in claim 1 wherein each of saidelectrodes comprises a generally flat portion and a cupshaped terminalportion the outer surface of which is positioned in one of saidapertures to define one side of the sparkgap in said aperture, saidpassageway being positioned over the inner surface of one of saidcup-shaped terminal portions thereby to maintain said impedance devicein position within said one cup-shaped terminal portion.

7. A sparkgap assembly as defined in claim 6 wherein said passageway isconcentrically positioned with respect to the cup-shaped terminalportion over which it is located and the open end of said passagewayadjacent said one cup-shaped terminal portion is smaller than the upperrim of the cupshaped terminal portion, thereby to assure a greaterelectrical sparkover length between the electrodes adjacent saidimpedance device through the passageway than through the sparkgapdefined by these two electrodes.

8. A sparkgap assembly as defined in claim 1 wherein said electriccircuit means comprises an integral resilient tongue on one of theelectrodes forming said one sparkgap, said tongue being resilientlybiased toward said impedance device and loaded in compression by contactwith it when assembled in operative position thereby to form aconductive circuit between said one electrode and one terminal of saidimpedance device and to resiliently bias a second terminal of saidimpedance device into conductive relationship with the other electrodeforming said one s arkgap.

9. A sparkgap assembly as de med in claim 8 wherein the electrode havingsaid integral tongue thereon comprises a base portion having three legsextending outwardly from one side thereof, said tongue being positionedin the area of said electrode including the middle leg and the part ofsaid base portion encompassed by an extension of the edges of saidmiddle leg therethrough.

10. A sparkgap assembly as defined in claim 9 wherein at least the outerend of said middle leg is positioned in a plane closer to the center ofsaid assembly than a common plane through the other two legs whereby anyflat conductive member placed on said two legs is prevented fromelectrically contacting said outer end of the middle leg.

11. A sparkgap assembly as defined in claim 9 wherein the electrodehaving said integral tongue thereon is mounted adjacent the outersurface of an end plate member in said stacked assembly of platemembers.

12. A sparkgap assembly as defined in claim 1 wherein said impedancedevice is a capacitor.

13. A sparkgap assembly for a surge voltage arrester comprising aplurality of stacked insulating plate members, means defining anaperture through each of said plate members, a plurality of sparkgapelectrodes mounted respectively adjacent opposite sides of said platemembers over said apertures thereby to form a sparkgap in each of saidapertures between adjoining electrodes, means spaced apart from saidaperture defining passageways through a predetermined number of saidplate members, a plurality of electrical impedance devices, at least oneof said impedance devices being mounted respectively in at least two ofsaid passageways and maintained in a relatively fixed position by thewalls thereof, and electrical circuit means connecting each of saidimpedance devices in shunt relation respectively with one of saidsparkgaps.

14. A sparkgap assembly as defined in claim 13 wherein at least one ofsaid impedance devices is a capacitor and another of said impedancedevices is a resistor.

15. A sparkgap assembly as in claim 14 wherein at least one capacitorand one resistor are mounted in one of said passageways and electricallyconnected in parallel with one another.

16. A sparkgap assembly as in claim 15 including at least one additionalimpedance device electrically connected in series with saidparallel-connected capacitor and resistor, said additional impedancebeing mounted in a separate passageway and electrically connected inshunt relationship with another sparkgap of the assembly.

* t i i

1. A sparkgap assembly for a surge voltage arrester comprising aplurality of stacked insulating plate members, means defining anaperture through each of said plate members, a plurality of sparkgapelectrodes mounted respectively adjacent opposite sides of said platemembers over said apertures thereby to form a sparkgap in each of saidapertures between adjoining electrodes, an impedance device, electricalcircuit means connecting said impedance device in shunt relation withone of said sparkgaps, means spaced apart from said aperture defining apassageway through the plate member separating the electrodes formingsaid one sparkgap, said impedance device being mounted in saidpassageway and maintained in a predetermined relatively fixed positionby the walls thereof.
 2. A sparkgap assembly as defined in claim 1wherein said passageway is longer than the length of said one sparkgapthereby to prevent sparkover of said passageway when a surge voltage isdischarged through the sparkgap assembly.
 3. A sparkgap assembly asdefined in claim 1 including a resistor mounted in said passageway andelectrically connected in shunt relationship with said impedance device.4. A sparkgap assembly as defined in claim 1 wherein said circuit meanscomprises an electrically conductive spring that is resilientlycompressed between said impedance device and one of the electrodesforming said one sparkgap when assembled in operative position therebyto form a conductive circuit between said one electrode and one terminalof said impedance device and to resiliently bias a second terminal ofsaid impedance device into conductive relationship with the otherelectrode forming said one sparkgap.
 5. A sparkgap assembly as definedin claim 4 wherein said spring is a leaf spring, and including holdingmeans for retaining said leaf spring in its operative position, saidholding means comprising means defining an elongated channel in thesurface of the insulating plate member immediately adjacent the leafspring, said channel being wide enough to allow the spring to becompressed without being retarded in such movement by the sidewalls ofthe channel but being narrow enough to prevent the spring from beingrotated more than 45*.
 6. A sparkgap assembly as defined in claim 1wherein each of said electrodes comprises a generally flat portion and acup-shaped terminal portion the outer surface of which is positioned inone of said apertures to define one side of the sparkgap in saidaperture, said passageway being positioned over the inner surface of oneof said cup-shaped terminal portions thereby to maintain said impedancedevice in position within said one cup-shaped terminal portion.
 7. Asparkgap assembly as defined in claim 6 wherein said passageway isconcentrically positioned with respect to the cup-shaped terminalportion over which it is located and the open end of said passagewayadjacent said one cup-shaped terminal portion is smaller than the upperrim of the cup-shaped terminal portion, thereby to assure a greaterelectrical sparkover length between the electrodes adjacent saidimpedance device through the passageway than through the sparkgapdefined by these two electrodes.
 8. A sparkgap assembly as defined inclaim 1 wherein said electric circuit means comprises an integralresilient tongue on one of the electrodes forming said one sparkgap,said tongue being resiliently biased toward said impedance device andloaded in compression by contact with it when assembled in operativeposition thereby to form a conductive circuit between said one electrodeand one terminal of said impedance device and to resiliently bias asecond terminal of said impedance device into conductive relationshipwith the other electrode forming said one sparkgap.
 9. A sparkgapassembly as defined in claim 8 wherein the electrode having saidintegral tongue thereon comprises a base portion having three legsextending outwardly from one side thereof, said tongue being positionedin the area of said electrode including the middle leg and the part ofsaid base portion encompassed by an extension of the edges of saidmiddle leg therethrough.
 10. A sparkgap assembly as defined in claim 9wherein at least the outer end of said middle leg is positioned in aplane closer to the center of said assembly than a common plane throughthe other two legs whereby any flat conductive member placed on said twolegs is prevented from electrically contacting said outer end of themiddle leg.
 11. A sparkgap assembly as defined in claim 9 wherein theelectrode having said integral tongue thereon is mounted adjacent theouter surface of an end plate member in said stacked assembly of platemembers.
 12. A sparkgap assembly as defined in claim 1 wherein saidimpedance device is a capacitor.
 13. A sparkgap assembly for a surgevoltage arrester comprising a plurality of stacked insulating platemembers, means defining an aperture through each of said plate members,a plurality of sparkgap electrodes mounted respectively adjacentopposite sides of said plate members over said apertures thereby to forma sparkgap in each of said aPertures between adjoining electrodes, meansspaced apart from said aperture defining passageways through apredetermined number of said plate members, a plurality of electricalimpedance devices, at least one of said impedance devices being mountedrespectively in at least two of said passageways and maintained in arelatively fixed position by the walls thereof, and electrical circuitmeans connecting each of said impedance devices in shunt relationrespectively with one of said sparkgaps.
 14. A sparkgap assembly asdefined in claim 13 wherein at least one of said impedance devices is acapacitor and another of said impedance devices is a resistor.
 15. Asparkgap assembly as in claim 14 wherein at least one capacitor and oneresistor are mounted in one of said passageways and electricallyconnected in parallel with one another.
 16. A sparkgap assembly as inclaim 15 including at least one additional impedance device electricallyconnected in series with said parallel-connected capacitor and resistor,said additional impedance being mounted in a separate passageway andelectrically connected in shunt relationship with another sparkgap ofthe assembly.